High price of Melbourne's hot weather

Tom Arup

HOT weather in Melbourne is set to cost the city on average $46.5 million a year to the middle of the century, unreleased economic research has found.

The study commissioned by Melbourne City Council, undertaken by consultancy AECOM, found projected total costs for 2011-2051 for the Melbourne municipality due to hot weather - heatwaves, the urban heat island effect, and single hot days - will be $1.86 billion.

While the analysis will not be made public for several months, a submission to a Senate committee investigation into extreme weather by the city council said the costs will be borne through transport delays, increased energy demand, health impacts and increased mortality, anti-social behaviour, and impacts on plants and animals.

A spokesman for the council told Fairfax Media the impacts of climate change on heatwaves and the urban heat island effect - dense city infrastructure increasing temperatures - had been included in the study. But any extra costs linked to rising temperature due to climate change were not separately estimated.

The Melbourne City Council's submission to the Senate investigation also said separate research into projected rising sea levels across Port Phillip Bay - to be released next month - finds the yearly costs of damage to properties at Southbank from inundation will rise from $3 million to $20 million a year by 2100.

''Modelling indicates that the City of Melbourne will be increasingly subjected to extreme weather events in the form of flooding and intense storms, hot days and heatwaves, [and] droughts due to the impacts of climate change,'' the council's submission says.

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''These events will impose increasing economic costs on the city as well as place the safety of residents and property at higher risk.''

The submission also refers to social research carried out by the council across 2011 and 2012 that surveyed 400 residents, 250 business and 100 visitors about their preparedness for climate change and extreme weather events.

It found 35 per cent of residents and 49 per cent of businesses perceived a risk from extreme weather, with a third from each group unsure. The survey found almost all residents surveyed believed in climate change but most said they were unprepared for very hot days and for flooding.

In its submission to the same Senate inquiry, the Bureau of Meteorology said that while it is problematic to blame a single weather event on climate change, recent observational evidence indicates increases in the frequency of extreme weather events as would be expected with global warming.

The bureau said that in Australia the frequency of very high temperatures has increased while the frequency of very low temperatures has decreased, with the changes occurring during both the day and night.

''Since 1990, strong trends have emerged in the occurrence of record-high maximum and minimum temperatures for Australia, with particularly large numbers in the decade from 2001 onwards,'' the bureau said.

''Over the period 2001-11, the frequency of record-high temperatures is now running at 2.8 (for maximum temperature) to 5.2 (for minimum temperature) times the rate of record low temperatures.''

The bureau says it is very likely the observed trend towards hotter temperatures will continue, and, depending on the rate of greenhouse gas emissions, will potentially accelerate under future global warming.